The present invention relates to a communication device, a communication method, a program and a communication system, and particularly relates to a communication device, a communication method, a program and a communication system capable of reducing power consumption.
A near-field wireless communication system performing contactless wireless communication in a near field by using an IC (Integrated Circuit) card is widely used. For example, applications as an electronic ticket and electronic money are well known. Recently, a cell phone including functions of the electronic ticket and the electronic money is becoming popular.
In the near-field wireless communication system, there exist a proximity-type IC card system prescribed as ISO/IEC 14443, a vicinity-type IC card system prescribed as ISO/IEC 15693, a NFC (Near Field Communication) prescribed as ISO/IEC 18092 and the like. ISO/IEC 18092 is a standard of NFCIP (Near Field Communication Interface and Protocol)-1.
There are an active mode and a passive mode in the near-field wireless communication by ISO/IEC 18092. The active mode is a communication mode in which electromagnetic waves are outputted in plural communication devices which transmit and receive data, and data is transmitted by modulating the electromagnetic waves. In the passive mode, one communication device (initiator) in the plural communication devices outputs an electromagnetic wave and data is transmitted by modulating the electromagnetic wave. Another communication device (target) in the plural communication devices transmits data by performing load modulation of the electromagnetic wave outputted by the initiator.
A “PCD” (Proximity Coupling Device) which is a reader/writer of ISO/IEC 14443, a “VCD” (Vicinity Coupling Device) which is a reader/writer of ISO/IEC 15693 and an initiator in the passive mode of ISO/IEC 18092 form a so-called RF (Radio Frequency) field (magnetic field) by generating the electromagnetic wave. An IC card of ISO/IEC 14443 (PICC), an IC card of ISO/IEC 15693 (VICC) and the target of ISO/IEC 18092 receives power supply by electromagnetic induction when coming close to the reader/writer or the initiator and can perform data transmission with respect to the reader/writer or the initiator.
Accordingly, it is necessary that the reader/writer of ISO/IEC 14443 and ISO/IEC 15693 and the initiator of ISO/IEC 18092 continue generating the electromagnetic wave for a long period of time with the main aim of supplying power to the IC card or the target. Therefore, there is a problem that power consumption of the reader/writer and the initiator is increased. For example, when the cell phone having functions of the reader/writer or the initiator performs output of the electromagnetic wave as described above, operable time which is 200 hours to 600 hours in just a normal stand-by state will be reduced to less than 1/10.
Various studies concerning techniques for reducing power consumption have been made until now (for example, JP-T-2008-533604, JP-A-11-126240 and JP-A-11-338984 (Patent Documents 1 to 3)).